People have a right to keep their private medical information private. No special reason should be needed, expected, or asked for. And no one should be given any crap for exercising their right to privacy.
As Edge says, too, there's a big middle ground. I wasn't in a position to cut all ties and move to a new place. How many are?
So there's people who know me first-hand from before transition. Those people now personally know a trans man. I know at least two of them have changed the way they treat trans issues, in a positive way.
Some of those people have unavoidably told others, so there's a circle of second-handers. Wouldn't surprise me if there's some amount of third-handers. Lo and behold, I'm not answering the paper-or-plastic question with "... and I'm transgender" (ha!) and there's a difference, however small, in public knowledge.
I bet every single one of us makes a difference just by doing what we need to do.
